not know one's arse from one's elbow
01
to show a great lack of intelligence or poor judgment
Dialect
British
British
![{not} [know] {one's} arse from {one's} elbow definition and meaning](https://cdn.langeek.co/photo/44844/original/?type=jpeg "{not} [know] {one's} arse from {one's} elbow definition and meaning")
例子
Not knowing his rase from his elbow, he stepped forward to lecture me. I suppose there is no end to the depth of some people's idiocy.
